Organo-tin aminocarbamate catalyst for preparation of polyurethane foam

ABSTRACT

A PROCESS FOR PRODUCING A POLYURETHANE FOAM BY REACTING A POLYALKYLENE GLYCOL WITH AN ORGANIC DIISOCYANATE IN THE PRESENCE OF A BLOWING AGENT AND A CATALYTIC AMOUNT OF AN ORGANO-SUBSTITUTED TIN AMINOCARBAMATE.

United States Patent U.S. Cl. 260-25 AC 7 Claims ABSTRACT OF THEDISCLOSURE A process for producing a polyurethane foam by reacting apolyalkylene glycol with an organic diisocyanate in the presence of ablowing agent and a catalytic amount of an organo-substituted tinaminocarbamate.

This is a division of application Ser. No. 196,841, filed Nov. 8, 1971,now abandoned which is a division of application Ser. No. 43,296 filedApr. 23, 1970, now Pat. No. 3,697,477 which is a division of applicationSer. No. 604,139, filed Dec. 23, 1966, now Pat. No. 3,520,910.

This invention relates to a new class of organotin compounds.

These compounds have been found particularly useful as catalysts in theroom temperature curing of silicone rubbers derived fromhydroxy-terminated methylpolysiloxane fluids. They are applicable alsoas intermediates and as catalysts in the preparation of urethane foams.

A compound conforming to the invention may be considered anorgano-substituted tin aminocarbamate wherein the tin atom is linked tothe carbamic nitrogen atom, by which is meant the nitrogen atomcorresponding to the nitrogen atom in carbamic acid (NH COOH).Altematively, such as compound may be defined as a fully substitutedstannane comprising one or both of the groups III-O OzN=CRR or BIT-C ONRR R R in which R is a hydrocarbon group, as alkyl or aryl.

In general, the compounds herein are embraced by the in which R is ahydrocarbon group, X is from the class :ORR and R (where R again is ahydrocarbon group), and R is selected from the class consisting ofhydrocarbon groups, oximo groups, diorganoaminooxy groups, the halogens,alkoxy groups, and

where R and X have the same significance as before indicated. For use ascatalysts in the above-mentioned applications, the compounds preferredare those in which each of the Rs connected to the tin is a butylradical and R is chlorine.

The compounds of the invention are for the most part condensationproducts of alkyl and aryl isocyanates with monoand bis-ketoximo anddiorganoaminooxy stannanes:

RNCOzR R RaSn(ONRR) RNCO RzSn-N-COzNRR NCOzR N-COzNRR Such reactions arein general carried out to best advantage in the presence of a suitablehydrocarbon solvent as benzene, toluene, ligroin, and the like. Thereactions proceed at room temperature, but higher temperatures may beemployed to increase the reaction rate. In any case, anhydrousconditions should be maintained throughout the reaction.

The detailed practice of the invention is illustrated by the followingexamples which are not to be taken as in any way limitative thereof:

EXAMPLE I 7.43 g. of tributylacetoximostannane (Bu SnON=CMe wasdissolved in 30 ml. of ligroin in a vessel filled with nitrogen andequipped with a magnetic stirrer, addition funnel, reflux condenser andthermometer. Thereafter, an equimolar amount (2.44 g.) ofphenylisocyanate, also dissolved in 30' ml. of ligroin, was added slowlyover 25 minutes with stirring. A slight temperature rise was notedduring the addition which was followed by a one-hour reflux period at apot temperature of about 70 C. The solvent was then removed in vacuo,leaving a viscous, pale-yellow residue, which was examinedspectroscopically. The infrared frequency characteristic of the moietyhad entirely disappeared with the development of an ester-type carbonylfrequency. Furthermore, the N.M.R. spectrum was in compliance with thecompound Bu SnNC Ph O-N=CM93 in accordance with the reaction:

BuaSnON=CMeg PhN=C=o Bu ShN-C O2N=CMe1 EXAMPLE II An experiment wasperformed in which only one oximo group on a dioximo-substituted tincompound was reacted, i.e.,

The apparatus was as described in Example I, the order of addition,however, being reverseda crucial factor. Thus, 3.97 g. (10.6 m. moles)of Bu Sn(ON=CMe was dissolved in 30 ml. of ligroin and 1.29 g. (10.8 m.moles) of phenylisocyanate in 30 ml. of ligroin thereafter added withstirring. After solvent removal, no N=C:O bond was detectable in theinfrared spectrum. The N.M.R. spectrum showed that one oximo group, MeC=NO-, was still attached to the tin.

EXAMPLE HI The above experiment was repeated, but instead of a 1:1 molarratio of PhNCO to Bu Cn(ON=CMe a 2:1 ratio was used. This produced thefully substituted compound (I) Bu 0 Me C=N--Oi3N%nN(ii-ON=CMeg Ph Bu Phas shown by spectroscopic techniques.

EXAMPLE IV 19.2 g. of Bu Sn(Cl) (ON=CMe dissolved in 100 ml. of benzenewas introduced into a nitrogen-flushed reaction vessel of the typedescribed previously, and -6.7 g. of phenylisocyanate, also dissolved inbenzene, was added dropwise and with rapid stirring. The resultantproduct was isolated by evaporation of the solvent. Analysis by infraredand N.M.R. techniques proved it to be EXAMPLE V Under conditions similarto those previously detailed n-Bu Sn(OMe) (ON=CMe is reacted with anequimolar amount of PhNCO to obtain B 112 S n-NC O N=C Me;

oMe Ph EXAMPLE VI The reaction:

Irz S n(OBu) [ON=G (Me) (Et)[ ZEtNCO (EtXMe) C=NO Et Pt Et was performedby adding a benzene solution of the tin compound (22.0 g., equivalent to0.0605 mole) to a similar solution of ethyl isocyanate (8.6 g., 0.121mole). The reaction mixture was heated at 50 for one hour whereafter aninfrared spectrum was taken of the solution. The N=C=O frequencies haddisapepared entirely. The N.M.R. spectrum ,showed shifts for the alkoxyand the ketoximo hydrogens, indicating that these groups had beendisplaced from the tin atom, yielding as the product i r 0 (Et) (Me)C=NOi3NSinlTI O Bu Et Pr Et EXAMPLE VII A hydroxy-terminateddimethylpolysiloxane fluid of 3520 cs. viscosity was intimately blendedwith a conventional cross'linker, commonly known as Ethyl Silicate 40,in a weight ratio of to 6. To this mixture one gram of the compoundprepared according to Example III (Buss n III--ON=CME :I

was added with stirring. Elastomeric properties were evident in theproduct after 20 minutes air-exposure. A fully cured elastomer resultedin 45 minutes. The odor of the rubber was acceptable and the rubber didnot have the corrosive properties often encountered with such rubberswhen cured using conventional tin catalysts.

EXAMPLE VIII EXAMPLE IX All of the following were found to be active ascuring agents for the rubber prepared as per Example VII:

Me20=N Ph N (Et) OOzN=C Me BUzSnN(Ph) COzN OM62 EXAMPLE X Application ofthe tin compounds in the production of polyurethane foam:

g. of a polypropylene glycol is mixed with 9 g. of methylene chloride ina plastic-coated paper cup by means of a mechanical stirrer. 2.25 g. ofa commercial polyurethane surfactant known as L520 is then smoothlyblended-in, whereafter 1.0 g. of

is added, followed by rapid stirring for about 20 seconds. Next,tolylenediisocyanate (63 g.) is poured in rapidly with an additionalstirring time of 8 seconds. The resulting foaming mixture is rapidlytransferred to a paper mold in which the foam is allowed to rise to fullexpansion. A 10 minute residence in an oven at 275 F. yields ahighquality expanded form.

EXAMPLE XI A 50 ml., B-necked flask was fitted with a magnetic stirrer,reflux condenser, addition funnel, thermometer, and nitrogen inlet. Tothe nitrogen-flushed apparatus were sequentially added with stirring3.27 g. of phenylisocyanate in ml. of ligroin and 5.61 g. of Bu Sn(O-NEtin 15 ml. of the same solvent. A 6 C. temperature rise was noted. Themolar ratio of the reactants was 2:1, so as to permit of the reaction:

After refluxing and vacuum stripping, the reaction was proved byinfrared spectra, which showed the absence of any isocyanate bond andthe presence of the characteristic carbonyl bond. The product compoundwhen tested as per Example VII supra was found to be catalyticallyactive.

EXAMPLE XII When EtNCO and Bu Sn(Cl)ONEt in 2:1 molar ratio were reactedin a manner similar to Example XI, one mole equivalent ofethylisocyanate Was recovered, evidencing that the Sn-Cl moiety is inertunder such conditions. The product BuzSn-N-C O N E Z:

yields an excellent RTV silicone rubber when employed as a curingcatalyst.

EXAMPLE XIII Addition of Bu Sn(OMe) (ONEt to an exces ofphenylisocyanate yielded the compound ONEliz BllzSn ON=CM62 was reactedin a 1:1 molar ratio with phenylisocyanate to obtain For this result, itappears essential that the isocyanate be added slowly in dilute solution(e.g. toluene) to an equal- 7 1y dilute solution of the tin compound.

6 EXAMPLE XV The following compounds were prepared following the usualprocedure:

All were active as RTV silicone rubber curing catalysts, although thefirst-listed compound was less than the others.

The invention claimed is:

1. An improved process for producing urethane foam by reacting apolyalkylene glycol with an organic diisocyanate in the presence of ablowing agent, said improvement comprises adding thereto a catalyticamount of a compound of the formula:

in which R is a hydrocarbon group, X is selected from the classconsisting of =CR and RR in which each R is a monovalent hydrocarbonradical and R is selected from the class consisting of hydrocarbongroups, oximo groups, diorganoaminooxy groups, the halogens, alkoxygroups and where R and X have the same meaning as above.

2. The process of claim 1 wherein each of the two Rs directly connectedto the tin atom is a low molecular weight alkyl group and the Rconnected to the nitrogen atom is a phenyl radical.

3. The process of claim 2, wherein R is chlorine.

4. The process of claim 2 wherein each of the R's connected to the tinatom is a butyl radical.

5. The process of claim 2 wherein R is an alkoxy group.

6. The process of claim 2 wherein R is an oximo group.

7. The process of claim 2 wherein R is in which R is the same as aboveand X is selected from the class consisting of =CRR and RR.

References Cited UNITED STATES PATENTS 3,164,557 1/1965 Merten et al.2602.5 AC 3,520,910 7/1970 Lengnick et al. 260429.7 3,697,477 10/1972Lengnick et a1. 26046.5 G

DONALD E. CZAJA, Primary Examiner M. I. MARQUIS, Assistant Examiner U.S.Cl. XIR.

0 260- NC, 77.5 AC

